The present invention aims to provide a means by which a cured product to be obtained has a low dielectric loss tangent and higher heat resistance. Specifically, provided are an active ester compound represented by chemical formula (1): (where in chemical formula (1), Ar1 is a substituted or unsubstituted first aromatic ring group, and each Ar2 is independently a substituted or unsubstituted second aromatic ring group, in which at least one of Ar1 and Ar2 has an unsaturated bond-containing substituent, and n is an integer of 2 or 3), a curable composition containing the active ester compound, and a cured product thereof.